I have a Raiden Fighters 2 Seibu SPI board. When it boots, I get a 'checksum error 6561' error.

Any idea how to fix this, or what's wrong? It seems it might be a region issue.

I checked the last byte of the PRG0 ROM, and it was the Japanese version code. I changed this to 10 for the US, and the error message changed to English, but nothing else changed. I tried both settings on JP121 jumper (the 'update' jumper).

Recently got an SPI mobo and a couple games myself. Got really scared for a while, since Raiden Fighters Jet was the only game that didn't work on it, but I figured it out eventually: the idiot seller sent me a Raiden Fighters Jet with the case installed upside-down (in hindsight, that's probably why I had such trouble getting it onto the mobo). Granted, I should have noticed that the labels on the chips visible through the vents were upside down compared to the game label, and Seibu probably shouldn't have designed the case or game PCBs so that they can be installed upside-down...

Anyway, I doubt any of this applies to these checksum errors, I just wanted to rant a bit.

I also was initially confused when my PVM showed 576i and displayed the games with huge black borders on all sides, but then I remembered that some arcade games have weird refresh rates, and sure enough the Seibu games use 54 or 55hz or something like that, which I assume makes my PVM think it's receiving a PAL signal, and it adds borders to make up for the difference in resolution between NTSC and PAL. But no big deal as I can just hit the Overscan button to zoom in.

The software i.e. the program ROMs might be too old for this motherboard so it does not recognize the SSXD 2.1 PCB.Maybe try burning the newest version from MAME into PRG 0,1,2,3 and changing the region byte ?

Today I've released a patch that will allow you to restore your motherboard to the original region (or whatever region you want, really). I made it because I had this exact same problem, hopefully less people will have to deal with it.

For what it's worth "checksum error" and "hardware error" both mean the region/game ID is corrupt. One means the region doesn't match, the other means the power was turned off in the middle of update and the region and/or game ID have been corrupted (I forget which is which).